I had planned to go out to Poldhu in Cornwall for CQ 160 CW last year (2013) but the plans were shelved when I instead went to meet interesting people and talk amateur radio in Oulu, Finland with the OH8X folks.
Three years ago I was looking for a place where I could do a multi-effort for ARRL CW from the British Isles with some friends. I found GB2GM on the West Coast of the Lizard in Cornwall in the SW of England. That is the site where Marconi made his first transatlantic transmissions. We thought that would be a suitably historic location for the ARRL contest and as it turns out it is also a great location. Only neighbouring building is an old hotel that has been redeveloped into a Care Home for old people. Noise level is low, there are several acres of fields outside the little club house/museum and it all sits on a plateau that then steeply (30m?) finishes right by the sea with a free take-off to the west.
I have never done a dedicated 160m contest before – only picked up useful multipliers in all-band contests – but the band is challenging and thus interesting. This would be a field-day-style expedition. There are no really useful antennas on site but there are a couple of 60ft lattice masts and there is space and a good shack. I need to bring almost everything I need as I make the 6 hour drive out to Cornwall.
The ambition is not to win – I have no illusions about being able to compete with the superstations when they are manned by good and experienced top band operators. I see the opportunity to focus on 160 for a full contest weekend as a great opportunity to learn more about the band and propagation and an opportunity to play with antennas. I wanted in particular to compare simple transmit antennas and some major receive antennas.
The location is exposed, right on the edge of a plateau say 60ft above the sea. Strong turbulent winds are tough on the antennas and on those who try to set them up. I was going to be alone and I’m no longer an 18-year old monkey so there had to be an element of practicality and realism to the whole project.
It is fun to plan and strategize. After a fair bit of that I decided to use two transmit antennas, a vertical and a horizontal, in order to play with the different characteristics and the impact on performance. The dipole would be a pretty low inverted V with the apex at 60ft broadside to 300 deg which is US. The vertical would be based on one of my 18m spiderbeam GRP poles and the simplest way to get some top loading is an inverted L configuration. I have the hardware and radials on cable drums from earlier expeditions. I’ll try to get the base as close to the cliff and the sea as the guying geometry would permit. The top L wire will be placed such that I get a slight antenna directivity towards the US.
For receive I have earlier used a 180m long beverage towards 300deg (US) on this site and would do that again but I will try to get it further south, away from the buildings. But I need more directions for the CQ contest so I decided to experiment with an 8-circle array. Now there is much to say about those but after modelling and some consideration about practicalities I decided to use active elements. Field layout and a desire to not get literally on top of the surrounding cattle fencing and my other wires dictated the location and a circle radius of the order of 30-50m. A prepared spreadsheet will help me get the dimensions and locations right on site when I can verify my estimates from Google Earth. My linear distance estimates based on Google Earth were excellent by I noticed that the elevation data was off. I assume Google Earth is using a course grid for elevation and simply interpolates in between thus not catching steep cliffs for instance.
My plan was to leisurely make the preparations in good time but plan and reality does rarely agree. Following my ZD8M excursion for CQWW in November family and other social commitments were the priorities through December and the Holidays and that kept me off all things radio. I thus found myself spending the weekend before the contest cutting aluminium and acetal sheet, drilling holes and preparing bolts with wingnuts for quick assembly of the receive array. I got some angle aluminium to use as a base stakes and earth stakes, delrin/acetal plates as base insulator (I wanted minimum capacity to ground in order not to lose signal) and telescoping aluminium tubes for the verticals. I had organized active antenna preamps – or rather impedance converters – from Hi-Z some time ago.
Besides the cutting I drilled 112 holes and assembled M3 and M6 bolts and washers and wingnuts to fit. Then I desperately ran around finding and building other bits and pieces needed for the station.
The weather can be pretty awful at this exposed site so in order to provide some margins I had decided to drive out on the Monday before the contest. That was wise. Tuesday turned up with rain, rain and rain plus 30mph wind. Well, there was more indoor work to do so all well so far. It turned out that the weather this time was worse than awful. As I write this from the cottage I use as a base on Sunday afternoon before the band opens up for the last evening of the contest the winds are gusting 50-60mph but it has at least stopped raining. It remains to be seen whether any antennas are still in place when I get back to the shack.
To cut a long story short I managed to get the outdoor work finished on Friday afternoon. The weather was atrocious throughout the week (the locals call it normal) and it was only mad dogs and a crazy radio amateur to be seen on the outside. The trick is to maximize the dry moments and there were a few of those. I also got some great help from a couple of club members; I could not have raised the 18m vertical on my own in those winds and it is so much more fun to work with nice company.
The fields outside the little museum are frequently stocked with a large heard of grazing young cows. They had gracefully been moved somewhere else but the cattle had left loads and loads of souvenirs on the soaking wet fields. There is much I don’t understand in this world starting with electromagnetics and modern particle physics all the way to human stupidity such as fighting wars instead of making love and to that list I now have to add the cow mystery: how can cows produce so much dung from so little grass?
Come Thursday evening and I was so exhausted that I was ready to knock on the door to the Care Home in order to check if they could take care of me. Friday came with a wet, windy, misty, grey start that could not have been bettered by Hollywood if they desired such an atmosphere. But the worst rain stopped and I could finish the work; repair the wind-hit inverted L for the second time, finish the beverage, lay out the control cable, cut the delay line, install the phasing and switch box for the 8-circle. With that done I just needed to tune the inverted L matchbox but now I had lost a little pig-tail needed for the fabulous little SARK-110 VNA and I had left my old MFJ259 in the cottage where I was staying. Time lost but pigtail found in the end – at the bottom of a deep pocket in my wind jacket.
At 4pm it was all working. It was time to check how well it was working. I put a small signal on the vertical/inv L and started to listen on the 8-circle. Oh the relief and joy I felt when IT WORKED! Even a very first quick check suggested that the rear patterns on the 8-circle seemed to be smooth and clean and down 15-30dB on the front. Wow! This is a low-noise location but I could hear and DF some noise that appeared to come from the area. There were a couple of weak noise spurs that came from the Care Home or the shack building. There was some that sounded like spurs/IM from a BC station coming from the east. All of it was weak so it would be covered by the night-time noise when the band opens up.
I had planned to spend a couple of days doing serious tests and measurements with these antennas before the contest but those days were now gone due to the weather issues.
The aim of this adventure was antenna experiments and not to set a record score in the contest so I decided to take it easy and rather play with the antennas during the contest. To that effect I did mostly S&P the first night. Wow! That 8-circle receive antenna in this quiet location really was a star performer. I could compare it directly with my 500ft beverage towards the US and the 8-circle was better on all accounts. I could compare it by listening on the inverted V dipole and the inverted L and the 8-circle opened up a new layer of stations to be heard. First DX I could hear when the band opened on Friday afternoon were a ZL and a couple of JAs – all buried in the noise on the dipole and inverted L. When NA opened up the 8-circle beat the beverage which had served us very well during two ARRL contests – the subjective impression was that the side- and back pattern of the 8-circle was cleaner and left me with less interference from behind.
It would soon become evident that my receive capability now was so good that I had created two new problems for myself.
Towards the end of the first night I was so tired that I fell asleep a couple of times. I decided to try running. With 15-30dB front-to-rear and the array pointing to NA I missed fairly strong callers from Europe on my back! My plan had been to set up for SO2R primarily in order to be able to listen better and simultaneously in different directions but problems with one of the radios prevented that. A small irritation: when switching directions the 12V to the active amplifiers/impedance converters at the base of the elements is also switched with associated loud cracks and that didn’t help. It might be OK for a DXer but not for snappy contesting. If I do this gain I need to build a smarter switching arrangement.
The other problem was that I could hear much better than I could be heard. My Inverted L and my Inverted V both worked. A few RBN tests confirmed that they worked as expected with the vertical (inv L) with its 40 radials close to the cliff outperforming the dipole almost universally but the dipole was useful and not dramatically worse. I ran full UK power on my Elecraft KPA500 and the RBN reports suggested that I was doing OK. But I spent the night calling a very large number of stations in NA/Caribbean that I could hear well but they just CQ’d back in my face. There were two very strong stations in KS and NM that were 20-25dB above noise almost all night. They never heard any of my many attempts to call them. There was a C6 station I also heard all night, perhaps 5-15dB above the noise floor and he just kept CQing. They were just two examples. I only managed to work a fraction of the stations I could hear, perhaps as little as 20% and this was with 400w out to decent antennas. I will do a further RBN analysis to compare my signal strength with other Europeans before drawing final conclusions but it certainly felt like a lot of stations transmit with good power into reasonably good antennas but can’t listen correspondingly – the receive antenna is as important as the transmit antenna and I am sure that local noise is an additional problem for many. But surely it doesn’t seem smart to transmit big and listen small – that is real pollution. In my case I now seemed to be unbalanced the other way around – hearing everything better than most but not being heard.
When building arrays for transmit the phasing is not that critical. Forward gain is pretty insensitive to the finer points of amplitude and phase balance. It is a different ballgame for receive however. There you don’t need the gain but you want the cancellation off your back and sides and to get that you need attention to phase and amplitude balance between the elements. For this vertical receive array I settled on a 40m radius and made up a template of PE line to get the element locations right. The elements were all made of 4 telescoping sections of Aluminium tube making them 3.7m tall and then there was 10cm connection to the active antenna buffer and a further 20cm to ground/earth. The field where the antennas were located was flat and looked quite homogeneous. Judging from measurements on the vertical transmit antenna ground connectivity appeared to be surprisingly high probably due to the high water content and salt spray from the sea (or minerals in the cow dung?). My assumption was that ground on the site was poor because there is only a fairly thin (1ft/30cm?) layer of soil above the base rock. Feed lines and the delay line were cut with the help of a VNA. The RX array was a high-risk project – I had not had time to check things out beforehand. I had for instance not checked the amplifiers/impedance converters (they shouldn’t be amplifiers really, just FET source-followers with high input impedance) so I did a quick check of each box with a simple short wire. One of the amps was off the scale in output noise level so I put it aside – I could do that because in a rare moment of foresight I had acquired a couple of spare amps.
When I had settled down after the chock and joy of having the practical implementation of the receive array actually agreeing with theory I pursued some further simple tests. Daytime noise floor was such that neither the array nor the beverage needed any amplifiers. The noise floor was highest on the inverted L and also high on the dipole. It was fun to watch the noise build-up as the D layer disappeared with the sun. In darkness there was a noticeably higher noise floor level in the sector NE to SE from this far SW location in England, just as expected really.
I spent most of the first night of the contest doing S&P and listening. Listening here was not like listening on top band from my suburban London QTH, it was quiet and a real joy. I got the subjective feeling that I could hear better than most and the complementary/conjugate feeling that I was weaker than most on transmit. A quick check on RBN showed that I was doing OK on transmit but the receive capability made it feel different.
I was knackered after a physically tough week and I needed a break for a quick nap during the first night and then I slept well through Saturday with the alarm set so I could check things out at the station before sunset on Saturday. It turned out that I needed that time. The Inverted L had snapped again in the gale-force winds but luckily such that it was easy to repair. The L needed to be retuned and that was “interesting” in the stormy weather. Some of the elements of the RX array needed some love and care to have them stand upright again.
On the second night I managed to work a few of those western hemisphere stations that couldn’t hear me the first night. The weather forecasters had warned about strong winds building up for the weekend and more heavy rain. I could hear that they were right as the night went on. The howling of the wind and the rain hammering on the building created a special atmosphere. As the band closed on Sunday morning I was happy to see note that the antennas were all working. I went back to my cottage accommodation and to sleep but was being kept awake by the noise from the howling wind. When I got back to the site on Sunday afternoon the 18m GRP pole supporting my Inverted L vertical had snapped just above midpoint. There was no way I could repair the mast under these weather conditions. It was tough to even walk across the field to inspect the damage. The pole has seen some use over the years and I guess it was material fatigue after the formidable hammering by the wind. I inspected the number 2 TX antenna (the inverted V dipole) and it appeared to be OK visually and it was also OK when I checked it on the coax end in the shack. Some of the receive verticals were again almost horizontal so some work was required. Working out on the field reminded m about working on the deck of a sail-boat in a gale. The main difference is that on a sailboat there are plenty of grab rails – not so among the dung heaps.
So it got dark and I started leisurely to listen and do a bit more S&P and attempts to run. I always have difficulties finding a run frequency. I am one of those who always end up last boarding an aircraft or a bus and similarly when I have carefully checked a frequency with a ? followed by a QRL? inevitably someone else has already occupied the real estate I had my eyes on.
After less than an hour the SWR on the dipole hit the ceiling whatever that ceiling is after a long coax run. Something had happened to my dipole – the wind must have hit it somehow. My immediate instinct was of course to grab some light and make the long walk out to the tower carefully avoiding the cow dung. But then I got a much better idea that made my spirit raise. Why not call it a day, take off to the local pub, enjoy a better part of the cows in the form of a steak and sit back and plan the next crazy adventure.
In the end I spent close to 20 hours on the radio instead of the 30 planned and I didn’t have time to do the more systematic measurements I had planned but I am still glad I did it. That 8-circle receive array is a star! Some RBN analysis in due course will tell me more about the transmit antenna performance relative other UK participants.
Now pray for me that the weather will somehow allow the take-down tomorrow Monday so I can drive back home on Tuesday early in order to catch my flight to SM0 and then continue to the annual CCF weekend which this year happens in Tallinn in ES-land.
I am planning to be back on 160 from the same site for ARRL CW and will then dump the beverage and only use a 4-element broadside array of two endfire cells for RX and since my 18m pole is no more probably a low vertical loaded with a T top. If the weather forecast is bad again I would however head straight for the pub and not bother with the contest or the antennas – you grow wise with your experiences.